If you’re researching standards for workplace ventilation and how to comply with them, this page is a good resource.
Efficient Ventilation for Safe Workplace Air
As a business owner or manager, it is important to consider the role of ventilation in both worker safety and productivity. Clearly, heat exposure can be dangerous to the health and well-being of workers and it also impedes their performance. Therefore, it is important to monitor and validate the ventilation in workplace HVAC systems.
1. Standards Related to Workplace Airflow and Safety
Environmental airflow, ventilation, and heat related hazards, as well as the employer’s duty to protect workers are covered in the Federal Occupational Safety and Health Act and various OSHA standards as follows:
- 29 CFR 1910 Subpart G, Occupational health and environmental control
- 29 CFR 1910.94, Ventilation.
- 29 CFR 1926 Subpart D, Occupational health and environmental controls
- 29 CFR 1926.57, Ventilation
2. Finding Airflow Deficiencies
Below, we will be covering methods for measuring airflow and testing ventilation. But, before we get into that, let’s consider some of the some of the “usual suspects” in terms of workplace airflow deficiencies and excessive or hazardous heat. These include:
- Confined Spaces
- High Occupant Density
- Spaces without Windows
- Facilities Designed for Maximum Energy Efficiency
- Spaces with Heat-Producing Equipment
3. Benefits of Good Indoor Air Quality
With a clear goal of eliminating stagnant air the focus should be on efficiently moving air through the supply and exhaust of the HVAC system. This is how industrial facilities and workplace environments are maintained for worker or occupant comfort and safety. The benefits are:
- Worker Comfort and Safety
- Control of Airborne Contaminants
- Prevention of Fire and Explosion
- Temperature and Humidity Control
- Worker Productivity
- Minimization of Odors
According to scientific studies, 71° F, which is at the center of the “comfort zone”, is an ideal target temperature for increasing worker productivity and performance. Maintaining temperatures near this target temperature throughout multiple work spaces or zones in a facility requires measuring and monitoring air velocity in HVAC systems and conducting leakage tests to maximize airflow efficiency. To that end, we’ll discuss the required instrumentation and then the proper use of this equipment.
4. Airflow Measurement & Pattern Analysis Tools & Instruments
Embedded Airflow Sensors and Switches including the F-Series and S-Series from Degree Controls Inc, measure air velocity, humidity and air temperature and are often placed within HVAC ductwork to test and monitor airflow in real-time.
A Sensor Pole Array, such as the °C SPAR from Degree Controls, Inc., is instrument with multiple airflow sensors inside a pole built according to customer-defined lengths. By mounting the °C SPAR to a telescoping base, a user can take readings at different heights and create an X-Y planar airflow analysis in a room. This technique is also useful for evaluating thermal stratification and the effectiveness of mixing air to achieve temperature equalization in your space. We will convey suggested measurement techniques using °C SPAR in HVAC dusts further in this article.
A Grid Airflow Sensor System, like the °C Grid from Degree Controls, Inc., is a pre-built, X-Y sensor array within an aluminum frame The °C Grid is used to study planar airflow profiles in rooms, ducts, HEPA filtration units, and airflow dampers. °C Grids are built with up to 200 sensors, each measuring air velocity and air temperature simultaneously.
Single-Point Sensors, like the UAS1000 series from Degree Controls, Inc., are individual airflow, temperature and humidity sensors that can be connected together with a data acquisition instrument called °C Port. This instrument along with AccuTrac™ data-logging software, allows the user to position the sensors to create custom, multi-point sensing arrays that determine airflow patterns as well as velocity and temperature distributions.
Air Flow Pattern Visualization Instruments, such as °C Breeze and FlowMarker™ fog generators by Degree Controls, Inc., are used HVAC technicians to detect leaks in ducts, monitor turbulence in ventilation systems and test HEPA filters.
5. Airflow Measurement Standards
Now that we’ve discussed some of the measurement devices for airflow, we’ll move on to the proper use of these sensors for testing, verifying, and monitoring the efficiency of HVAC systems. In order to validate that minimum ventilation rates are being met, airflow sensors such as the F200, F300, F400, or F500 can be embedded in ducts.
Volumetric airflow measurement accuracy depends on the location of these sensors and ASHRAE recommends placing them at least 7.5 duct diameters downstream and 3 duct diameters upstream from obstructions or changes in airflow direction. Accurate and reliable readings, require the sensor to be placed in stable, laminar flow:
- Away From Bends or Junctions in Ducts
- Away From Turbulence (caused by fans, filters or other heating and cooling devices)
Additional Placement Recommendations Here
6. Multipoint Arrays for In-Duct Airflow Measurement
In a cross-sectional area of a duct, air velocity and temperature can vary. So, multi-point sensors like the °C SPAR improve testing accuracy by taking measurements at multiple points and calculating the mean. Guidance on the number of sensor points required within a plane for circular and rectangular ducts is provided by ASRAE. They specify a minimum of 25 sensor points for square or rectangular ducts and 18 sensor points for circular ducts. See Diagram Above.